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Abstract:

A microencapsulated formulation of pendimethalin comprising an alkali or
an alkaline earth metal salt of an organic acid. Also described are
processes for the preparation of the formulation and a method of
controlling weeds at a locating by using the described formulation.

Claims:

1. A capsule suspension formulation of pendimethalin comprising a
herbicidally effective amount of microencapsulated pendimethalin, the
microcapsules comprising said herbicidally effective amount of
pendimethalin being encapsulated within a polymeric wall, said polymeric
wall being in-situ formed by an interfacial polymerization reaction
occurring between a first phase dispersed in a second phase, at least one
of said first and second phases being characterized in comprising a
pre-defined amount of at least one alkali or alkaline earth metal salt of
an organic acid.

2. The formulation as claimed in claim 1, having a reduced staining
property over an encapsulated pendimethalin formulation comprising an
inorganic salt.

3. The formulation as claimed in claim 1 or claim 2, wherein said first
and second phases are immiscible with each other.

4. The formulation as claimed in any one of the preceding claims, wherein
said first phase is an organic phase dispersed in said second phase.

5. The formulation as claimed in claim 4, wherein said second phase is an
aqueous phase.

6. The formulation as claimed in any one of the preceding claims, wherein
said polymeric wall is selected from polyurea, polyurethane, polyamide,
polycarbonate, polysulfonamide and crosslinked or non-crosslinked
combinations thereof.

7. The formulation as claimed in claim 6, wherein the capsule polymeric
wall is a polyurea wall.

8. The formulation as claimed in any one of the preceding claims, wherein
said polymeric wall is formed by an interfacial polymerization triggered
by contacting a first wall forming component with a second wall forming
component.

9. The formulation as claimed in claim 8, wherein said first and second
wall forming components, being same or different, are included within at
least one of said first and second phases.

10. The formulation as claimed in claim 8, wherein said first wall
forming component is selected from polyisocyanate, polyacid chloride,
polychloroformate and polysulfonyl chloride.

11. The formulation as claimed in any one of claims 8-10, wherein said
second wall forming component is selected from polyamine and polyol.

14. The formulation as claimed in any one of the preceding claims,
wherein said first wall forming component is present in an amount of
about 0.1% to about 20% by weight of the organic phase.

15. The formulation as claimed in any one of the preceding claims,
wherein said second wall forming component is present in an amount of
about 0.3% to 7.5% by weight relative to the total weight of the
formulation.

16. The formulation as claimed in claim 7, wherein said polyurea shell
wall is formed by a self-condensation reaction of a polyisocyanate wall
forming component.

18. The formulation as claimed in any one of the preceding claims,
wherein alkali or alkaline earth metal moiety of said alkali or alkaline
earth metal salt of an organic acid is selected from sodium and
potassium.

19. The formulation as claimed in any one of the preceding claims,
wherein said alkali or alkaline earth metal salt of an organic acid is
sodium acetate or disodium succinate.

20. The formulation as claimed in any one of the preceding claims
comprising 0.2% to about 5% by weight of a surfactant selected from
ethoxylated lignosulfonic acid salts, lignosulfonic acid salts, oxidized
lignins, lignin salts, salts of styrene-maleic anhydride copolymers,
polyvinyl alcohol, salts of partial esters of styrene-maleic anhydride
copolymers, partial salts of polyacrylic acid and partial salts of
polyacrylic acid terpolymers.

21. The formulation as claimed in any one of the preceding claims wherein
said alkali or alkaline earth metal salt of an organic acid or mixtures
thereof is present in an amount of from about 2% to about 55% by weight
of the formulation.

22. The formulation as claimed in any one of the preceding claims
comprising from about 5% to about 60% of pendimethalin active ingredient.

23. The formulation as claimed in any one of the preceding claims,
wherein said polymeric shell wall constitutes from about 1% by weight to
about 20% by weight of the formulation.

24. The formulation as claimed in any one of the preceding claims,
wherein said microcapsules have a particle size of about 2 micrometers to
about 50 micrometers.

25. The formulation as claimed in any one of the preceding claims,
additionally comprising at least one excipient selected from an anti-foam
in an amount of about 0.01% to about 5% by weight of the formulation, a
rheology modifier in an amount of about 0.01% to about 3% by weight of
the formulation, a mineral acid from about 0.1% to about 10% by weight of
the formulation and a biocide in an amount of from about 0.01% to about
3% by weight of the formulation.

26. A process for the preparation of a capsule suspension formulation,
said process comprising: a. forming an aqueous solution comprising at
least one surfactant and a pre-defined amount of at least one alkali or
alkaline earth metal salt of an organic acid; b. forming an organic phase
by melting a herbicidally effective amount of pendimethalin active
ingredient and adding a predetermined amount of polyisocyanate wall
forming component; c. dispersing said organic phase in said aqueous
solution to obtain an emulsion to form an interface between the discrete
droplets of organic phase and the aqueous phase; and d. maintaining said
emulsion for a sufficient period of time to allow substantial completion
of the self-polymerization reaction of polyisocyanate such that said
liquid droplets in the organic phase are converted to capsules comprising
polyurea shells enclosing pendimethalin active ingredient.

27. The process as claimed in claim 26, wherein said polymeric shell wall
is polyurea wall formed by a self-condensation reaction of a
polyisocyanate wall forming component.

28. The process as claimed in claim 26 or claim 27, wherein said emulsion
of said organic phase in said aqueous solution is heated to a temperature
of between 20.degree. C. to about 100.degree. C.

29. The process as claimed in any one of the claims 26-28, wherein the
polymeric shell wall is formed by dispersing the organic phase droplets
in the continuous aqueous phase to form an emulsion followed by heating
the emulsion resulting therefrom; or heating the continuous aqueous phase
and dispersing the organic phase droplets in the heated continuous
aqueous phase to form the emulsion thereby effecting the desired
self-condensation reaction at the interface between the organic droplets
and the aqueous phase.

30. A process for the preparation of a capsule suspension formulation,
said process comprising: a. forming an aqueous solution comprising at
least one surfactant and a pre-defined amount of at least one alkali or
alkaline earth metal salt of an organic acid; b. forming an organic phase
by melting a herbicidally effective amount of pendimethalin active
ingredient and adding a predetermined amount of a first wall component to
said organic phase; c. dispersing said organic phase in said aqueous
solution to obtain an emulsion; and d. adding a second wall forming
component to said emulsion such that said second wall forming component
reacts with said first wall forming component comprised within said
emulsion to polymeric wall encapsulating at least said herbicidally
effective amount of pendimethalin active ingredient.

31. The process as claimed in claim 30, wherein said first wall forming
component is added to molten pendimethalin while stirring.

32. The process as claimed in claim 30 or claim 31 additionally
comprising neutralizing the reaction mixture with an inorganic acid.

33. The process as claimed in any of the claims 30-32, wherein the step
of adding a second wall forming component to the emulsion is carried out
at a temperature of about 35.degree. C. to about 85.degree. C.

34. A method for controlling undesirable plant species at a locus, said
method comprising applying to the desired locus a herbicidally effective
amount of a microencapsulated pendimethalin formulation as claimed in
claims 1-24 or a capsule suspension formulation obtainable by the process
claimed in claims 24-32.

[0002] Pendimethalin is a dinitroaniline herbicide having chemical formula
[n-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine). It was first
registered for use in the United States in 1974. It is a selective
herbicide which controls certain broadleaf weeds and grassy weed species
in crop and non-crop areas. It is applied to soil preplant, preemergence,
and postemergence with ground and aerial equipment.

[0003] Pendimethalin is an orange yellow crystalline solid with a melting
point of 54-58° C. It is soluble in chlorinated hydrocarbons and
aromatic solvents such as methylene chloride, acetone and xylene.
Pendimethalin is stable under acidic and alkaline conditions.

[0004] Pendimethalin is currently available in various different
agrochemical formulation types such as emulsifiable concentrate (21.9% to
42.3%), liquid (34.4%), granular (0.7% to 2.0%), soluble
concentrate/liquid (22.0%), water dispersible granules, dry flowable (up
to 60.0%), capsule suspension and wettable powder (50.0%). Thus, there
are many formulation choices available to a formulator setting out to
prepare a desired formulation of pendimethalin.

[0005] The different formulations applicable to an agrochemical differ in
their effectiveness on the desired weeds, effects the tolerance of the
turf and ornamentals to the herbicide, differ in their cost advantages,
differ in the drift potential of the herbicide and also differ in the
ease of application and compatibility with the application equipment.
Another challenge to the skilled formulator is the selection of an
appropriate surfactant. Surfactants are known to increase the rate of
absorption of the herbicide in the weedy species but also increase the
potential for plant injury to the desirable plants during herbicide
drift. Yet another challenge before a skilled formulator setting out to
obtain a formulation containing pendimethalin is selecting either a
granular or a sprayable formulation.

[0006] Pendimethalin has been conventionally available in both granular
and sprayable forms, which may differ in the degree of weed control.
However, it is often advantageous to obtain a sprayable formulation
containing certain herbicides due to inherent advantages of a sprayable
formulation.

[0007] The granular formulations exhibit relatively low foliar absorption
because most of the applied granules fall through the leaf canopy to the
soil below. In contrast, sprayable products achieve good coverage and
adhere better to the foliage, providing relatively good weed control. It
has also been observed that a granular product comprises a greater
relative amount of the inert ingredients comparative to a sprayable
formulation. Thus, the amount of the formulated product to deliver the
same dosage of the active ingredient is much greater with granules
resulting in higher shipping and packaging costs.

[0008] An advantage of the sprayable formulation over granules is more
uniform application achieved with the sprayable formulations. The
granular formulations are usually difficult to apply uniformly,
especially those that contain a relatively high concentration of active
ingredient. Thus, it is more often advantageous to formulate sprayable
formulations of certain agrochemicals.

[0009] However, phytotoxicity of some of the sprayable formulations
including pendimethalin has been reported. It is desirable to provide
formulations containing pendimethalin that do not display or reduces the
extent of phytotoxicity.

[0010] Another challenge that relates to dinitroaniline herbicides,
pendimethalin in particular, is the potential for staining the sidewalks
and other locations where the herbicide is applied. The active ingredient
herbicides of the dinitroaniline class have a yellowish or
yellowish-orange color. It is further known that granular formulations
often do not stain badly, whereas a liquid formulation may cause more
serious staining. Moreover, granules are easy to sweep or blow from
concrete surfaces, whereas overspray need to be washed off before it
dries. Thus, it is desirable to provide sprayable formulations containing
pendimethalin that substantially reduce the incidence of staining.

[0011] U.S. Pat. No. 4,871,392, discusses under the background thereof,
that pendimethalin is known to exist in polymorphic forms as orange and
yellow crystals. This patent further discusses that pendimethalin is a
pesticide that is difficult to formulate owing partly due to the unique
staining problems associated with pendimethalin. This patent further
discusses that the presence of pendimethalin in the orange macrocrystal
form results in large elongated crystals in final formulations. Moreover,
when pendimethalin in the orange macrocrystal form is found in
compositions, very large, elongated crystals (about 3000 microns in
length) appear in final product, resulting in instability, difficulty in
processing and unreliability of usage apart from the severe staining
further compounded by a severe clogging of nozzles.

[0012] U.S. Pat. No. 5,705,174 discloses microencapsulated pendimethalin
formulations i.e. an aqueous concentrate composition of pendimethalin
particles which are encapsulated by a polymeric wall material, which show
a reduced tendency to form large crystals. These compositions also have
improved storage stability. Unfortunately, it has been seen that
microencapsulation of pendimethalin tends to slow the release of the
active ingredient.

[0013] U.S. Pat. No. '174 teaches an aqueous capsule suspension
formulation of pendimethalin, which contains about 456 grams of active
ingredient per liter. The encapsulation of pendimethalin allows for the
elimination of organic solvents in the product. The elimination of
organic solvents reduces odor, staining to a certain extent, volatility
and surface residue adhesion as compared to existing emulsifiable
concentrate formulations of pendimethalin. Moreover, the
microencapsulated pendimethalin formulation is stable under conditions of
freezing and thawing and is compatible with liquid and dry fertilizer.
However, the existing problem of staining, phytotoxicity and
corrosiveness is not adequately addressed by the disclosure of U.S. Pat.
No. 5,705,174.

[0014] Moreover, this patent essentially teaches a microencapsulated
formulation of pendimethalin containing an inorganic salt, which is added
prior to microcapsule formation. It is disclosed that the addition of an
inorganic salt or mixtures thereof prior to the microcapsule formation
provides a visibly cleaner microcapsule as more of the colored active
ingredient is encapsulated, which is therefore unable to stain the
external surfaces of the microcapsules. These microcapsules are also
stated to be less prone to breakage than the microcapsules prepared by
the conventional methods. Examples of inorganic salts taught by this
patent are sodium chloride, calcium chloride, potassium chloride, sodium
nitrate, magnesium sulfate and/or sodium sulfate.

[0015] However, these inorganic salts are not without additional
disadvantages. The use of an inorganic salt such as sodium chloride even
to the extent of 0.1-0.5% has been shown to aggravate the already
existing phytotoxicity of pendimethalin. Sodium and chloride ions
contribute synergistically to salt toxicity in wheat, Biologia
Plantarium, 37 (2); 265-271, 1995, Martin et al., studied the effects of
supplying excess mineral salts, involving sodium as a cation and a range
of counter-anions, including chloride on the growth and photosynthetic
capacity of a salt susceptible bread wheat. It was found that the
synergistic effect of sodium and other alkali and alkaline earth metals
with chlorine shows that neither of these ions is alone responsible for
the salt stress induced damage in plants.

[0016] Moreover, these inorganic salts dissociate and/or dissolve in water
and increase the hardness of water. The increased water hardness further
reduces the temperature and suspension stability of microencapsulated
pendimethalin. Moreover, the polymeric capsule wall of the disclosed
microencapsulated pendimethalin is still susceptible to breakage to an
appreciable extent. Thus, the problem of staining continues to plague the
existing state of the art.

[0017] A need remains in the art for microencapsulated formulations of
pendimethalin having improved non-staining property with reduced
phytotoxicity problems. The present invention adequately addresses these
and other needs existing in the art.

ADVANTAGES OF THE INVENTION

[0018] Thus, an advantage of the present invention is a capsule suspension
formulation of pendimethalin that does not demonstrate any phytotoxicity
to the desirable plants.

[0019] Another advantage of the present invention is a capsule suspension
formulation of pendirnethalin that is substantially non-staining.

[0020] Yet another advantage of the present invention is a capsule
suspension formulation of pendimethalin which shows a reduced tendency to
form large crystals.

[0021] Another advantage of the present invention is a capsule suspension
formulation of pendimethalin that is storage stable.

[0022] Yet another advantage of the present invention is a capsule
suspension formulation of pendimethalin that is stable under conditions
of freezing and thawing.

[0023] Another advantage of the present invention is a capsule suspension
formulation of pendimethalin that does not suffer from capsule polymeric
wall rupture.

[0024] Yet another advantage of the present invention is a capsule
suspension formulation of pendimethalin that does not increase the
hardness of water.

[0025] Yet another advantage of the present invention is a capsule
suspension formulation of pendimethalin that does not appreciably corrode
the container.

[0026] Another advantage of the present invention is a capsule suspension
formulation of pendimethalin that avoids the need for an inorganic salt
or mixtures thereof.

[0027] The remaining portion of the description and claims offers at least
one of these and other advantages.

SUMMARY OF THE INVENTION

[0028] Thus, in one aspect, the present invention provides a capsule
suspension formulation of pendimethalin comprising a herbicidally
effective amount of microencapsulated pendimethalin, the microcapsules
comprising said herbicidally effective amount of pendimethalin being
encapsulated within a polymeric wall, said polymeric wall being in-situ
formed by an interfacial polymerization reaction occurring between a
first phase dispersed in a second phase, at least one of said first and
second phases being characterized in comprising a pre-defined amount of
at least one alkali or alkaline earth metal salt of an organic acid.

[0029] In another aspect, the present invention provides a process for the
preparation of a capsule suspension formulation, said process comprising:
[0030] (a) forming an aqueous solution comprising at least one
surfactant and a pre-defined amount of at least one alkali or alkaline
earth metal salt of an organic acid; [0031] (b) forming an organic phase
by melting a herbicidally effective amount of pendimethalin active
ingredient and adding a predetermined amount of polyisocyanate wall
forming component; [0032] (c) dispersing said organic phase in said
aqueous solution to obtain an emulsion to form an interface between the
discrete droplets of organic phase and the aqueous phase; and [0033] (d)
maintaining said emulsion for a sufficient period of time to allow
substantial completion of the self-polymerization reaction of
polyisocyanate such that said liquid droplets in the organic phase are
converted to capsules comprising polyurea shells enclosing pendimethalin
active ingredient.

[0034] In another aspect, the present invention provides a process for the
preparation of a capsule suspension formulation, said process comprising:
[0035] (a) forming an aqueous solution comprising at least one
surfactant and a pre-defined amount of at least one alkali or alkaline
earth metal salt of an organic acid; [0036] (b) forming an organic phase
by melting a herbicidally effective amount of pendimethalin active
ingredient and adding a predetermined amount of a first wall component to
said organic phase; [0037] (c) dispersing said organic phase in said
aqueous solution to obtain an emulsion; and [0038] (d) adding a second
wall forming component to said emulsion such that said second wall
forming component reacts with said first wall forming component comprised
within said emulsion to polymeric wall encapsulating at least said
herbicidally effective amount of pendimethalin active ingredient.

DESCRIPTION OF INVENTION

[0039] It has been surprisingly found that the presence of an alkali or
alkaline earth metal salt of an organic acid within the microencapsulated
formulation of pendimethalin provides a substantially non-staining
formulation. The term "substantially non-staining" herein denotes that
such formulations comprising an alkali or alkaline earth metal salt of an
organic acid demonstrates surprisingly reduced staining property by a
fraction of at least two to about five times in comparison with the
conventional formulations comprising an inorganic salt.

[0040] It has further been found that the microencapsulated formulations
according to the present invention comprising an alkali or alkaline earth
metal salt of an organic acid also reduce or eliminate the phytotoxicity
that was observed with conventional formulations comprising an inorganic
salt. Moreover, the addition of an alkali or alkaline earth metal salt of
an organic acid does not increase the hardness of water which was
observed with the conventional formulations thereby enhancing the
suspension stability of the resultant formulations. It was surprising
that use of an organic salt of an alkali or alkaline earth metal led to a
drastic improvement in the suspension stability of the formulations
according to the present invention. The present inventors have further
found that the presence of an inorganic salt was shown to corrode the
container while an organic salt did not corrode the container in which it
was placed. The formulations according to the present invention were
found to be storage stable. Without wishing to be bound by theory, it is
believed that the presence of an alkali or alkaline earth metal salt of
an organic acid further prevents the early rupture of the polymeric
capsule wall.

[0041] Accordingly, in one aspect, the present invention provides a
capsule suspension formulation of pendimethalin comprising a herbicidally
effective amount of microencapsulated pendimethalin, said microcapsules
comprising said herbicidally effective amount of pendimethalin
encapsulated within a polymeric wall, said polymeric wall being in-situ
formed by an interfacial polymerization reaction occurring between an
organic phase dispersed in an aqueous phase, said aqueous phase being
characterized in comprising a pre-defined amount of at least one alkali
or alkaline earth metal salt of an organic acid.

[0042] It should be understood however that said aqueous and organic
phases are not particularly limiting. The interfacial polymerization
reactions suitable for encapsulated formulations according to the present
invention may be prepared by reaction between the wall forming components
present in two substantially immiscible liquids, of which said organic
and aqueous phases constitute a preferred embodiment. Moreover, the two
walls forming components may be either same or different.

[0043] In another aspect, the present invention provides a process for the
preparation of a capsule suspension formulation, said process comprising:
[0044] (a) forming an aqueous solution comprising at least one
surfactant and a pre-defined amount of at least one alkali or alkaline
earth metal salt of an organic acid; [0045] (b) forming an organic phase
by melting a herbicidally effective amount of pendimethalin active
ingredient and adding a predetermined amount of a first wall component to
said organic phase; [0046] (c) dispersing said organic phase in said
aqueous solution to obtain an emulsion; and [0047] (d) adding a second
wall forming component to said emulsion such that said second wall
forming component reacts with said first wall forming component comprised
within said emulsion to polymeric wall encapsulating at least said
herbicidally effective amount of pendimethalin active ingredient.

[0048] The capsule polymeric wall of the present invention may be any
known shell wall material and is preferably selected from a polyurea, a
polyurethane, a polyamide, a polycarbonate, a polysulfonamide shell wall
or a crosslinked or non-crosslinked combinations thereof. Preferably, the
capsule polymeric wall is a polyurea wall.

[0049] The capsule polymeric wall of the present invention is formed using
interfacial polymerization by contacting said first wall forming
component with a second wall forming component as is conventionally known
in the art.

[0050] The first wall forming component is preferably selected from a
polyisocyanate, a polyacid chloride, a polychloroformate and a
polysulfonyl chloride. The second wall forming component is preferably
selected from a polyamine and polyol. Preferably, a polyisocyanate reacts
with a polyamine to form a polyurea capsule wall of the present
invention.

[0052] The preferred polyamines as the second wall forming components may
be selected from ethylenediamine, propylene-1,3-diamine,
tetramethylenediamine, pentamethylenediamine, 1,6-hexamethylenediamine,
diethylenetriamine, triethylenetetramine, tetraethylenepentamine,
pentaethylenehexamine, 4,9-dioxadodecane-1,12-diamine,
1,3-phenylenediamine, 2,4- and 2,6-toluenediamine and
4,4'-diaminodiphenylmethane or acid addition salt thereof. The preferred
polyamine according to the present invention is diethylenetriamine.

[0053] The first wall forming component comprises from about 0.1% to about
20% by weight of the organic phase of the present invention. The second
wall forming component is preferably present in an amount of about 0.3%
to 7.5% by weight relative to the total weight of the formulation.

[0054] In a further preferred embodiment, the preferred polyurea polymeric
shell wall may be formed by a self-condensation reaction of a
polyisocyanate wall forming component. In this embodiment, the process
for the preparation of the capsule suspension formulation according to
the present invention comprises establishing a physical dispersion of an
organic phase in the aqueous phase. In this embodiment, the organic phase
comprises the organic isocyanate intermediate such as hereinabove
described along with the pendimethalin active ingredient.

[0055] Thus, in another aspect, the present invention provides a process
for the preparation of a capsule suspension formulation, said process
comprising: [0056] (a) forming an aqueous solution comprising at least
one surfactant and a pre-defined amount of at least one alkali or
alkaline earth metal salt of an organic acid; [0057] (b) forming an
organic phase by melting a herbicidally effective amount of pendimethalin
active ingredient and adding a predetermined amount of polyisocyanate
wall forming component; [0058] (c) dispersing said organic phase in said
aqueous solution to obtain an emulsion to form an interface between the
discrete droplets of organic phase and the aqueous phase; and [0059] (d)
maintaining said emulsion for a sufficient period of time to allow
substantial completion of the self-polymerization reaction of
polyisocyanate such that said liquid droplets in the organic phase are
converted to capsules comprising polyurea shells enclosing pendimethalin
active ingredient.

[0060] In an embodiment, the emulsion of said organic phase in said
aqueous solution may be preferably heated to a temperature of between
20° C. to about 100° C., preferably to about 35-85°
C. to accelerate the self-condensation of the polyisocyanate pre-polymer.

[0061] However, irrespective of whether self condensation of the first
wall forming component is preferred or condensation between a first and a
second wall forming component is preferred, the relative quantities of
the organic and the aqueous phases are not critical for the process of
the present invention. Typically, the organic phase may comprise upto
about 75% by volume of the total emulsion and comprises discrete droplets
of an organic solution dispersed in the aqueous solution.

[0062] The droplet size in the emulsion was not found critical to the
formulation and process of the present invention but may be found between
0.5 microns to about 4000 microns, which may be further adapted using a
high shear device to preferably about 1 micron to about 100 microns. It
has further been found that the in situ self condensation polymerization
reaction is self terminating and is generally allowed to run to
completion. The reaction typically runs to completion within the span of
a few minutes to a few hours. In a preferred embodiment, the reaction is
typically allowed to run for about 2 to 3 hours.

[0063] However, the preferred polyurea polymeric shell may be formed by a
self-condensation reaction of a preferred polyisocyanate using other
preferred methods. In one such preferred embodiment, the formation of the
polyurea capsule enclosure around the dispersed organic droplets could be
brought about by (a) dispersing the organic phase droplets in the
continuous aqueous phase to form an emulsion followed by heating the
emulsion resulting therefrom; or (b) heating the continuous aqueous phase
and dispersing the organic phase droplets in the heated continuous
aqueous phase to form the emulsion thereby effecting the desired
self-condensation reaction at the interface between the organic droplets
and the aqueous phase.

[0068] Preferably, the surfactant is lignosulfonate of calcium or sodium.

[0069] Preferably, the surfactant is present in an amount of about 0.2% to
about 5% by weight of the formulation.

[0070] The aqueous solution of the present invention includes an alkali or
alkaline earth metal salt of an organic acid or mixtures thereof in an
amount of from about 2% to about 55% by weight of the formulation.

[0071] The term "herbicidally effective amount" of pendimethalin is that
quantity of pendimethalin which when applied in that amount will provide
the required control of weeds. The particular amount is dependent upon
many factors including, for example, the crop, weeds sought to be
controlled and environmental conditions. The selection of the proper
quantity of active agent to be applied, however, is within the expertise
of one skilled in the art and is not considered particularly limiting.

[0072] The microencapsulated formulations according to the present
invention comprise from about 5% to about 60% of pendimethalin active
ingredient.

[0073] In a preferred embodiment, the polymeric shell wall according to
the present invention constitutes from about 1% by weight to about 20% by
weight of the formulation. In another preferred embodiment, the polymeric
shell wall constitutes about 2.5% by total weight of the formulation.

[0074] The microcapsules of the present invention preferably have a
particle size of about 2 micrometers to 50 micrometers.

[0075] Preferably, the capsule suspension formulations of the present
invention comprise an anti-foam in an amount of about 0.01% to about 5%
by weight of the formulation. Such suitable anti-foams are conventionally
known in the art and are not particularly limiting.

[0076] The capsule suspension of the present invention may further include
a rheology modifier. The preferred rheology modifier includes xanthan gum
and clay, which may be present in an amount of about 0.01% to about 3% by
weight of the formulation.

[0077] The capsule suspension formulation according to the present
invention may further be neutralized with a mineral acid to regulate the
pH within the desired range. Accordingly, the formulations according to
the present invention additional comprises from about 0.1% to about 10%
of a neutralizing acid, which may be a mineral or an organic acid.
Preferably, the mineral acid is hydrochloric acid.

[0078] Another advantage of the addition of a neutralizing acid is that
the added acid combines with the unreacted amines to form an ammonium
salt, which substantially reduces the amount of external salt addition
required for achieving an appreciable non-staining property. The addition
of a neutralizing acid is particularly beneficial in reducing the level
of inorganic salt of the prior art formulations, which has been reported
to aggravate the problem of phytotoxicity in various tested plants. In
this embodiment of the present invention, a significantly large quantity
of amines in excess may be employed to further reduce the external
addition of a salt by in situ generation of a larger amount of salt upon
reaction with the neutralizing acid.

[0079] In a preferred embodiment, the formulations according to the
present invention may additionally comprise a biocide in an amount of
from about 0.01% to about 3% by weight of the formulation.

[0080] In another aspect, the present invention also provides a process
for the preparation of a capsule suspension formulation, said process
comprising: [0081] (a) forming an aqueous solution comprising at least
one surfactant and a pre-defined amount of at least one alkali or
alkaline earth metal salt of an organic acid and optionally heating said
aqueous solution; [0082] (b) forming an organic phase by melting a
herbicidally effective amount of pendimethalin active ingredient and
adding a predetermined amount of a first wall component to said organic
phase; [0083] (c) dispersing said organic phase in said aqueous solution
to obtain an emulsion and optionally heating said formed emulsion; and
[0084] (d) adding a second wall forming component to said emulsion such
that said second wall forming component reacts with said first wall
forming component comprised within said emulsion to polymeric wall
encapsulating at least said herbicidally effective amount of
pendimethalin active ingredient.

[0085] Preferably, said step of forming an aqueous solution comprises
heating tap water to an elevated temperature, preferably about 60°
C. and adding said surfactant and said alkali or alkaline earth salt of
an organic acid. In a preferred embodiment, an anti-foam is also added to
said aqueous solution.

[0086] In another preferred embodiment, said first wall forming component
is preferably added to said molten pendimethalin while stirring.

[0087] In yet another preferred embodiment, said step of dispersing said
organic phase in said aqueous solution to obtain an emulsion is carried
out to a desired particle size.

[0088] In another preferred embodiment, subsequent to the addition of the
second wall forming component to the emulsion, the reaction is allowed to
continue for a predetermined time, preferably one hour under stirring
while the reaction is maintained at an elevated temperature.

[0089] Subsequently, the reaction mixture is neutralized with an inorganic
acid, preferably hydrochloric acid. The neutralization is carried out
preferably to attain a formulation pH of from about 6.5 to about 7.5.

[0090] Subsequently, xanthan gum is preferably added under stirring.

[0091] In a preferred embodiment, a biocide is added to obtain the target
formulation.

[0092] In a preferred embodiment, the process of the present invention is
carried out at an elevated temperature to maintain the pendimethalin
active ingredient in a molten state and to enhance the rate of polymeric
wall formation. In this embodiment, the process of the present invention
is preferably carried out at a temperature of about 35° C. to
about 85° C., and is more preferably conducted at a temperature of
about 50° C. to 65° C.

[0093] The release rate of the formulations according to the present
invention preferably varied from about 100 ng to about 145 ng, while the
free active ingredient was measured from about 0% to about 0.2% by weight
of the formulation.

[0094] The invention further relates to a method for controlling weeds at
a locus by applying to the locus of the weeds a herbicidally effective
amount of a microencapsulated pendimethalin according to the present
invention or a capsule suspension formulation obtainable by the process
of the present invention.

[0095] Preferably, the present invention provides a method for controlling
undesirable plant species which comprises applying to the foliage of the
plants or to the soil or water containing seeds or other propagating
organs thereof, a herbicidally effective amount of a microencapsulated
pendimethalin of the present invention or a capsule suspension
formulation obtainable by the process of the present invention.

[0096] Yet another surprising advantage offered by the present invention
was the substantial reduction in the corrosive property. The formulations
according to the present invention did not require to be stored in
non-aluminum or non-metallic or non-epoxy containers, which was a severe
limitation on the packaging and transport of the prior marketed
formulations.

[0097] Advantageously, the microcapsule formulations prepared according to
the present invention or obtainable by the process of the present
invention may be used directly as herbicidal compositions or may be
diluted with water for use.

[0098] Alternatively, additional ingredients such as anti-settling agents,
pH-adjusters, anti-freeze agents and the like may be added to the
microcapsule compositions prepared by the process of the present
invention to form concentrated microcapsule herbicidal compositions
without departing from the scope of the present invention.

[0099] The invention shall now be described with reference to the
following specific examples. It should be noted that the example(s)
appended below illustrate rather than limit the invention. and that those
skilled in the art will be able to design many alternative embodiments
without departing from the scope of the present invention.

Examples 1, 2 and 3

[0100] An aqueous solution was created by heating tap water to 60°
C. while adding sodium acetate, then sodium lignosulfonate, then antifoam
while stirring. A sufficient quantity of water was separately preserved
for the amine and gum preparations. Meanwhile, organic phase was formed
by melting pendimethalin technical to 60° C. and then adding
polymethylene polyphenylisocyanante while stirring. The aqueous and
organic phases were maintained at 60° C. throughout reaction. The
organic phase was emulsified in the aqueous solution till the desired
particle size. DETA (amine) was added to the resultant emulsion. Reaction
was allowed to proceed for 1 hour while maintaining heat at 60° C.
under stirring. The reaction mixture was allowed to cool to ambient
temperature for 15 minutes before neutralizing with HCl. The formulation
was neutralized to pH 8.0 in cold conditions or at a pH of 7 in warmer
conditions. The neutralized formulation was filtered through a 60 mesh
sieve. A xanthan gum-water slurry was separately prepared and added to
the above formulation under strong stirring conditions for at least 15
minutes to have a complete development of the gum. Lastly, a biocide was
added. The particle size was measured using a Horiba LA-910. The
resultant formulation was compared to the properties of conventionally
marketed formulation.

[0101] Table 1 below is the composition of the formulation obtained by the
process described in the above process.

[0103] The staining measurements reported above were measured with the
help of a Hunter LabScan XE colorimeter. Each reported test was repeated
five times to confirm the staining or non-staining nature of the tested
samples on different samples and under different testing conditions. In
order to conclude the improvement in the non-staining properties of the
formulations of the present invention, staining tests were conducted on
duct tape and repeated to cloth tape to reconfirm the findings.

[0104] In the tests reported above, the colorimeter measured the staining
color left on the substrate by assigning three values L*, a* and b* to
the stain which corresponded to the lightness/darkness measurement,
redness/greenness measurement and the yellowness/blueness measurement
respectively. The differences between these measured for each tested
sample i.e. that according to the present invention and the
conventionally known sample and that of a standard sample were calculated
as delta (Δ) values respectively:

Δa*=a* (sample)-a* (standard), wherein +Δa* meant sample was
redder than standard and -Δa* meant the sample was greener than the
standard; Δb*=b* (sample)-b*(standard), wherein +Δb* meant
the tested sample was yellower than standard and -Δb* meant the
sample was bluer than standard; ΔL*=L* (sample)-L*(standard),
wherein +ΔL* meant the sample was lighter than the standard and
-ΔL* meant the sample was darker than the standard.

[0105] The total color or staining value, ΔE, was thereafter
calculated using the following formula:

ΔE=SQRT[(ΔL*)2+(Δa*)2+(Δb*)2]

[0106] A greater value of ΔE corresponded to a greater degree of
staining. The stain samples were prepared on cloth tape (Scotch Glass
Cloth Electrical Tape) or duct tape--(Tesa, BDF Beiersdorf White Duct
Tape). These tapes were chosen in order to investigate possible
differences in staining potential of the formulations on different
surfaces. The substrates consisted of 2 inch by 2 inch (5 cm by 5 cm)
squares cut from transparent paper with a piece of tape on the center.
Enough formulation was applied to the tapes to create a 3/4 inch (2 cm)
diameter circle. The formulations were left on the tape for 15 minutes
and then rinsed off completely with a water squirt bottle. Color/stain
testing was then performed within 30 minutes of when samples were rinsed.
Blank samples of tapes without formulation were tested first on the
equipment to subtract out color values inherent to the tapes themselves.
Stain samples were prepared in duplicate and each sample was measured
twice, once in a horizontal orientation and once in a vertical
orientation on the colorimeter to cancel the effects of the tape's
directional grain. This yielded four data points for each stain sample.
Therefore, the total staining measurement for the sample according to the
invention and for the conventional samples was calculated for cloth tape
and duct tape using the above formula. Without wishing to be bound by
theory, it was believed that pendimethalin having an intense staining
property, would tend to adsorb strongly on organic surfaces such as
polyester, cloth, paper etc. Hence, it was believed that a comparison of
the common surfaces such as first aid tape, cloth tape, duct tape would
provide a close reflection of actual staining a farmer would encounter as
a daily routine.

[0107] It was thus surprisingly found that the formulation according to
the present invention afforded a substantially non-staining formulation,
which was reduced by a fraction of about 5 or at least by a fraction of
about 2 comparative to the hitherto known formulation. Specifically, it
was surprisingly found that the formulation according to the present
invention displayed a staining DE of only 2.44 and 1.49 on cloth tape and
duct tape respectively, whereas the closest commercial formulation
displayed a staining measurement of 11.22 and 2.19 respectively. Without
wishing to be bound by theory, it is believed that the presence of an
alkali or alkaline earth metal salt of an organic acid prevents the
rupture of the polymeric capsule wall and reduces the staining property
of the conventional microencapsulated pendimethalin formulations.

[0108] Further staining tests were conducted on various substrates
comparing the staining property of the formulations according to the
present invention comprising other organic salts of alkali and alkaline
earth metals vis-a-vis the formulations comprising an inorganic salt.
Again, greater ΔE represented greater staining.

[0109] Table 3 demonstrates the cumulative stain value measurements total
for cloth tape and first aid tape for a formulation according to the
present invention comprising disodium succinate versus a commercially
available formulation comprising an inorganic salt, which is further
compared to a formulation substantially free of a salt. It was
surprisingly found that the formulation comprising disodium succinate
(8.600) was only half as staining as the commercially available
formulation (16.348).

[0111] Table 4 demonstrates the stain value measurements total for cloth
tape for a formulation according to the present invention comprising
sodium acetate versus a commercially available formulation comprising an
inorganic salt, which is further compared to a formulation substantially
free of a salt. It was surprisingly found that the formulation comprising
sodium acetate (2.780) was only a third as staining as the commercially
available formulation (7.453).

[0113] Table 5 demonstrates the stain value measurements for first aid
tape for a formulation according to the present invention comprising
disodium succinate versus a commercially available formulation comprising
an inorganic salt, which is further compared to a formulation
substantially free of a salt. It was surprisingly found that the
formulation comprising disodium succinate (4.380) was only half as
staining as the commercially available formulation (8.895).

[0115] FIG. 4 depicts a comparison of three separate sodium acetate
formulations having the same formulation vis-a-vis the staining measured
for commercial formulation measured on a duct tape. All three batches
comprising sodium acetate exhibited ΔE values of 1.14, 1.60 and
1.84 which was only about half of the ΔE exhibited by the
commercial formulation, 3.19.

[0116] FIG. 5 depicts a comparison of two separate sodium acetate
formulations having the same formulation vis-a-vis the staining measured
for commercial formulation measured on a first aid tape. The two batches
comprising sodium acetate exhibited ΔE values of 4.06 and 5.41
which was only about half of the ΔE exhibited by the commercial
formulation, 9.01.

[0117] FIG. 6 depicts a comparison of sodium acetate formulation vis-a-vis
the staining measured for commercial formulation measured on a paper
tape. The batch comprising sodium acetate exhibited ΔE values of
2.57 which was only about half of the ΔE exhibited by the
commercial formulation, 4.84.

[0118] FIG. 7 depicts a comparison of four separate sodium acetate
formulations having the same formulation vis-a-vis the staining measured
for commercial formulation measured on a cloth tape. The batches
comprising sodium acetate exhibited ΔE values of 2.21, 2.67, 2.93
and 6.05 which was only about one-third to about half of the ΔE
exhibited by the commercial formulation, 11.22.

Corrosion Resistance

[0119] The pendimethalin capsule suspension formulations were prepared
comprising about 15% of an organic salt of an alkali or alkaline earth
metal, which was compared with the commercial formulation containing 15%
sodium chloride. A stainless steel (dimensions: 6 inches by 1.5 inches)
strip was placed in the solutions comprising 15% of sodium chloride and
compared with formulations containing 15% of sodium acetate, sodium
oxalate, sodium succinate, sodium citrate and sodium sulfite
respectively. The strips were observed after 24 days storage at room
temperature.

[0120] It was surprisingly observed that corrosion was observed only in
sodium chloride solution whereas the remaining salt solution plates were
found corrosion free. The present invention thus readily solves the
container corrosion problem which was seen in the currently marketed
formulations.

Efficacy

[0121] The formulation according to example 3 above was tested against
annual grasses and certain broadleaf weeds. Tests were run to investigate
the phytotoxicity of the formulations of example 3 of the present
invention vis-a-vis the commercially available formulation. The dose of
application of the tested formulation was 1-4 quarts/acre prior to weed
emergence by diluting it with 10 gallons of water. The formulations were
applied using drop nozzles.

[0122] Initially, qualitative visual evaluation parameters were tested for
phytotoxicity. A numerical plant damage rating scale was used for
phytotoxicity determination on a scale of 0 to 10 where 0 represents no
phytotoxicity and 10 represents complete "kill". The description of the
individual plant scores are as hereunder:

[0123] These visual parameters for the evaluation of phytotoxicity were
crop lodging, epinasty and hyponasty, stunting of growth, nechrosis,
chlorosis or yellowing of crop, leaf blotch or scorching, spotting,
rottening, deformation in leaf shape and appearance and twig mortality or
leaflet curling. It was surprisingly found that the tested formulations
according to the present invention scored over the commercial formulation
over all these tested parameters. Apart from the qualitative parameters,
the formulations were also tested for the quantitative parameters like
the average height of the plant, average number of leaflets in the plant,
average fresh and dry weight of the plant and average length/width ratio
of the plants. It was surprisingly found that the tested formulations
according to the present invention scored over the commercial formulation
over all these tested parameters.

[0124] The comparative samples were diluted at different doses namely
1×, 2× and 4× along with the control on soybean at
three leaf stage. All the doses were sprayed homogenously on plots. Each
treatment was observed six times at day 0, 1, 3, 7, 14 and 28 days after
treatment. All experiments were replicated thrice to ensure statistical
accuracy. It was found that the formulation according to the present
invention was substantially non-phytotoxic in comparison to the
commercially available formulation.

[0125] A phytotoxicity evaluation of formulation without any salt,
formulation of Example 3 above vis-a-vis the commercial formulation
including an inorganic salt was carried out at 7 days after spraying. The
qualitative as well as quantitative parameters were critically observed
at appropriate times. It was found that the samples without a salt and
that according to example 3 showed similar non-phytotoxic effect on the
soyabean plant. These samples were not phyto-toxic at recommended and
double recommended doses, whereas at four times recommended dose
(4×), the formulation of Example 3 showed only slight phytotoxicity
to plant (curling of the leaf edge along with standing of growth). In
contrast, the commercially available formulation led to a noticeably
higher degree of phytotoxicity than the remaining samples. Further, the
plots sprayed with the commercial formulation exhibited less number of
plants as compared to corresponding other plots. Further, the growth of
the plants were retarded and various other phyto-toxic symptoms like mild
chlorosis, necrosis, leaf blotch/scorching and curling of the leaves were
observed in dose dependent manner on the commercial formulation sprayed
plots.

[0126] The observations were repeated at 15th day after application
of the sprays. It was observed that in the plots sprayed with the
formulation of example 3 and with the formulations without any salt, the
plants which showed minor phytotoxicity on the 7th day were found
fully recovered from the initial shock. In contrast, a higher degree of
nechrosis and chlorosis (yellowing of crop) and/or blotching or scorching
was observed in the plot sprayed with the commercial formulation even
after 15 days of application. The results of the phytotoxicity trials are
tabulated as hereunder:

[0129] Thus, it was found that the formulations according to an embodiment
of the present invention as well as a formulation without any salt were
substantially less phytotoxic, showed substantially less plant growth
stunting as compared to a commercially available formulation.

[0130] It was found that the maximum density of plant growth was observed
in the plot that was sprayed with the formulation of example 3, which was
almost comparable to the control plot or the plot sprayed with the
formulation without any salt. Surprisingly, the plots sprayed with the
commercial sample displayed the least plant growth density. It was
surprising that the presence of an alkali or alkaline earth metal salt of
an organic acid could lead to a substantial increase in the plant growth
density.

[0131] Wherein the aforegoing reference has been made to components having
known equivalents, then such equivalents are herein incorporated as if
individually set forth.

[0132] Accordingly, it will be appreciated that changes may be made to the
above described aspects and embodiments of the invention without
departing from the principles taught herein. Additional advantages of the
present invention will become apparent for those skilled in the art after
considering the principles in particular form as discussed and
illustrated. Thus, it will be understood that the invention is not
limited to the particular embodiments described or illustrated, but is
intended to cover all alterations or modifications which are within the
scope of the invention.

Patent applications by Christian Becker, King Of Prussia, PA US

Patent applications by Jaidev Rajnikant Shroff, Mumbai IN

Patent applications by Prakash Mahadev Jadhav, Mumbai IN

Patent applications by Vikram Rajnikant Shroff, Mumbai IN

Patent applications by UNITED PHOSPHORUS LIMITED

Patent applications in class The nitrogen and a nitro group bonded directly to the same benzene ring (e.g., nitroanilines, etc.)

Patent applications in all subclasses The nitrogen and a nitro group bonded directly to the same benzene ring (e.g., nitroanilines, etc.)